Method of welding wires under tension



y 9, 1956 R. ZAPHIROPOULOS METHOD OF WELDING WIRES UNDER TENSION 2Sheets-Sheet 1 Filed June 21, 1954 W E W W M m D W m N m 4 T H W "A P Twg 7 (/76 MOVEMENT if 5 22 :EII3 E In. T 5 47 IN V EN TOR. Pen/1 Zap/w'raoou/os f". Po g /o/v POgC/ /ON y 1956 R. ZAPHIROPOULOS 2,748,238

METHOD OF WELDING WIRES UNDER TENSION Filed June 21, 1954 2 Sheets-Sheet2 /8 ,1 f I 56 /5 3 U 5 U j I Z0 Z0 a: Y

:EIl3 5 :EI[5 E INVENTOR.

Ae/m Zaph/ropau/os Mmi llnited States METHGD OF WELDING WHRES UNDERTENSION Application June 21, 1954, Serial No. 438,153

8 Claims. (Cl. 219-10) The present invention relates to a method ofsecuring a plurality of conducting members to a metallic frame orsupport. More particularly, the invention relates to cathode-ray tubeshaving a grid of essentially parallel wires adjacent to a stripedphosphor screen, or target electrode, and to a method for so positioningthese wires as to permit the establishment of a desired relationshipbetween such wires and the phosphor strips of the screen.

Cathode-ray tubes constructed with a grid of essentially parallel wireslocated adjacent to a striped phosphor screen are now known in the art.Such a grid may form one component of an electron lens system whichserves to focus the beam electrons into a pattern of thin linesregistered with the phosphor strips of the screen. This PDF(post-deflection-focusing) type of cathoderay tube operation has beenset forth by Ernest 0. Lawrence and is illustrated by his U. S. PatentNo. 2,692,532, granted Otocber 26, 1954.

In order to facilitate an understanding of the features of the presentinvention, a brief description of one such form of single-gun PDF tubewill now be given. This description should be construed as exemplaryrather than limiting, since it will be seen that the invention isobviously applicable to tubes operating along different principles. Ingeneral, however, the tube may incorporate a screen, or targetelectrode, made up of a relatively large number of very narrowcomponent-color phosphor strips laid down in a predetermined sequenceand intended to luminesce, when impacted by the cathoderay beam, incolors such as red, green, blue, green, red, green, etc. Obviously, whenreference is hereinafter made to the color of a phosphor, what is meantis the color of the light emitted therefrom which reaches the eye of anobserver. The phosphors are then aluminized, or in some other mannerprovided with an electrically conductive coating.

A grid assembly is located adjacent to such a phosphor screen. The gridmay be made up of essentially parallel wires, and so related to thephosphor strips of the screen that, in an electron-optical sense, thereis a wire aligned with each blue strip, and similarly a wire alignedwith each red strip. The red wires are connected to a common terminal,while the blue wires are similarly joined together electrically.

Between the grid wire assembly and the conductive coating on thephosphor screen there may be established a relative difference ofpotential of such magnitude and polarity as to create a series ofconverging cylindrical electron lenses for the electrons in the scanningbeam. Such converging electrical fields cause the beam electrons to forma fine line pattern on the phosphor screen, this line structure havingno necessary direct geometrical relationship to the path covered by thescanning beam in tracing the lines of the raster area.

It will now be appreciated that as the beam electrons travel from theelectron gun, they may be focused by the above-described lens structureinto a series of lines associated with the phosphor strips. If there iszero atent O i 2,748,238 Patented May 29, 1956 potential differencebetwen the red and blue terminals of the wire grid, then these linesformed by the beam electrons will be caused to lie within the boundariesof the green strips. If the wires associated with the red strips aremade positive relative to the wires electron-optically related to theblue strips, the beam electrons will be deflected, and the thin lineswill now lie within the boundaries of the red strips. Similarly,electrons will strike the blue strips when the wires associated withsuch strips are relatively positive with respect to the red wires.Different component colors are thus displayed according to the potentialdifference (if any) existing between the two sections of the grid wireassembly. Accordingly, color control in a cathode-ray tube having a gridassembly of the above nature (whether used for PDF or not) is broughtabout by a cyclic change in the potentials applied to selected wires ofthe grid.

in designing one form of grid assembly in which the above principles areutilized, the wires thereof are maintained in position relative to thephosphor strips of the target by means of spacer elements, since thedistance between the grid wires and the phosphor-coated surface of thetarget is critical in many respects. One preferred construction in whichthe grid wires and the phosphor screen are formed as a single unit isillustrated and described in a United States patent to RennZaphiropoulos, No. 2,683,833, granted July 13, 1954.

In the Zaphiropoulos assembly, a light-transmissive base plate (whichmay be of glass) is employed as a target backing. This base plate issecured to a grid frame by the strand conductors, or wires, of the grid.A pair of spacer bars is afiixed to one surface of the base plate, anddefines a window, or target area, therebetween which may be coated withphosphor strips having the desired color characteristics. Means areprovided for securing the electrically-conducting wires to the frame sothat these wires extend across the window, or target, area of the baseplate and are positioned therefrom by the spacer bars. Inasmuch as thegrid structure is designed for color switching, or micro-deflection, ofthe beam in the vicinity of the target electrode, the wires or linearconductors are divided into two sets of alternate strands, and suitablemeans are provided for applying potentials to each set of strands. Tocarry this out, the frame is divided into two sections, with eachsection serving a separate set of strands and also being electricallyinsulated from the other. Consequently in this form of construction theglass plate is sandwiched between the wires of the grid, on one hand,and the two frame sections on the other. together by the tension of thewires associated with the. outer frame portion, and this pressure actsto hold the frames, base plate, and wires in a unitary assembly.

The color grid structure set forth by Zaphiropoulos in hisabove-mentioned patent is completely satisfactory insofar as operationis concerned, and produces an image in which there is no colorcontamination. Nevertheless, it is somewhat time-consuming tomanufacture due to the techniques which must be employed. As preferablyconstructed, each set of grid wires is attached to its associated framesection by hooking the wire over a projection on the frame, laying downthe wire across the raster area of the base plate, hooking it over aprojection on the opposite side of the same frame, bringing it backacross the raster area of the base plate, and so on. A winding operationis thus carried out which, while producing a grid of satisfactoryoperating characteristics, nonetheless requires a considerable amount oftime to complete and hence materially reduces the number of units whichmay be manufactured within a given time period.

In an attempt to shorten the time required for fabricat-, ing such colorgrid structures, an alternative method was These two frame sections arepressed devised. This is set forth both in the above-mentioned patent ofRenn Zaphiropoulos, No. 2,683,833, as well as hi further application,Serial No. 307,436, filed Sep tember 2, 1952. This consists of windingthe grid continuously around the base plate to eliminate thebackand-forth motion previously employed. Inasmuch as this leaves a setof wires on the rear, or viewing, side of the base plate which have tobe removed prior to operation of the tube, it is necessary to anchor thewires near the two extremities of the base plate. This is done bycementing them in position so that the portion of each turn of wirewhich is unnecessary to tube operation may be cut out and discarded.Although eliminating one objectionable feature of previous methods ofconstruction, this lastmentioned technique adds a step of cementing thewires in position, and, furthermore, all of the tension of the wires insuch a construction is exerted through these ccmentitous bindings. Inaddition, winding of the grid by such a method still requires aconsiderable period of time inas much as each wire strand is woundindividuall A further step in the development of grid structures of thetype under consideration is to extend the idea set forth immediatelyabove and at the same time eliminate the necessity for retaining thewires in position by a cementitious substance, as well as to reduce by aconsiderable amount the time necessary for completion of the gridstructure. These objectives are carried out by utilizing awire-positioning apparatus which utilizes spools of wire equal in numberto the number of wires desired on the finished grid. The continuousconductors obtained by unwinding all of these spools of wireconcurrently are caused to extend in substantially parallel fashion.Furthermore, a tensioning device is provided for this set of continuousconductors, so that the wires, which lie in substantially parallelrelationship, are maintained under a degree of tension approximatelyequal to that whicn is desired for the finished grid wire assembly. Ametal frame section is then brought into contact with this set oftensioned wires in such a manner that the two oppositelydisposedsections of the frame contact the set of grid wires at the precisepoints necessary to assure parallel alignment of the wires following anattachment of the wires to the frame section.

In other words, the frame section is laid against the set of parallelwires so that the wires extend across the window area of the frame. Atpoints where the individual wires cross the two frame sections, theformer are welded to the frame, with these welds being made successivelyso that the frame is first welded to each wire of the set at that pointfurthest removed from the rolls or spools containing the continuousconductors. A similar welding operation is then carried out on theremaining frame member at two oppositely-disposed points, the wiresextending beyond the welds are cut off so as to leave a set of tensionedconductors extending across the open area of the frame and secured tothe two oppositely-disposed frame members.

The welding process hitherto performed upon the set of grid wires andthe frame section in order to secure these two units together is of thetype in which a pair of welding electrodes are placed so that one of theelec trodes underlies the lower surface of the frame section crossed bythe Wires, and the remaining electrode is brought into contact with thewire surface at a point opposite to that at which the wire contacts theframe. Qurrent is then passed through the wire and the frame side memberso as to effect a fusion of the wire metal to the metal of the frame.

A serious difficulty arose in carrying out the above operation, due tothe fact that, when the wire was spotwelded to the frame, the tensionunder which the wire was held caused the wire to break at the point ofthe weld. The reason underlying this action is that during the weldingoperation the welding current melts the wire metal, and consequently thestrength of the wire is reduced sub- 4' stantially to Zero during theactual welding time. As a result, the tension of the wire causes thewire to pull away from the welding area. The present invention disclosesan extremely simple method of preventing this wire breakage during thewelding operation, and one which requires substantially no additionaltime or effort.

One object of the present invention is to provide an improved processfor welding together metallic articles.

An additional object of the present invention is to provide an improvedprocess for Welding a plurality of grid wires to a metallic supportingframe.

An additional object of the present invention is to provide a process ofthe above nature in which breakage of the grid wires due to the weldingprocess is minimized.

A still further object of the present invention is to provide means forretaining a set of grid wires under tension during a welding operationso that melting of any particular grid wire during the welding processwill not result in breakage of that wire.

Other objects and advantages of the present invention will be apparentfrom the following description of a preferred form thereof and from thedrawings, in which:

Figure l is a perspective view of one form of apparatus by means ofwhich the method of the present invention may be carried out;

Figure 2 is a side view of Figure 1 showing an additional apparatus forconcurrently performing welding operations on two separate grid frames;

Figure 3 by its parts 3a, 3b, 3c shows the progressive movement of theframes;

Figure 4 is a plan VlW of a grid wire and frame assembly such as itappears after the process of the present invention has been completed;

Figure 5 is a side view of a modification of the apparatus of Figure l;and

Figure 6 is an end view of Figure 5.

Referring now to Figures 1 and 2 of the drawings, there is shown aplurality of spools of wire equal in number to the number of grid wiresdesired in the finished assembly. Only relatively few of these spoolshave been illustrated for the sake of clarity. These spools are arrangedside-by-side or in a matrix, so that the wires, when drawn from thespools and aligned, lie in substantially parallel fashion as bestillustrated in Figure 1. Furthermore, these parallel wires arepreferably but not necessarily substantially coplanar as again bestillustrated in Figure l. in order to accomplish this positioning and toinitiate the welding operation which is described herein, the end of thewire from each of these spools it) is secured by a clamp 12 which isonly made use of when the equipment is first set up for operation. ithas for its purpose the placing of the wires in the position best shownin Figures 1 and 2, where they are maintained under a desired degree oftension by suitable means such as the spring 14. The wires thus placedunder tension are drawn out from their respective spools by the wireclamp 12 until they are of sufiicient length to accommodate the weld ingapparatus which is now to be described.

The principal object of the present invention is to permit thecontinuous production of grid wire assemblies in a minimum period oftime and by a process which will be substantially automatic inoperation, thus requiring little or no personal attention. To achievethese objectives the following procedures are used: A grid frame in issupported in a movable jig which travels in a direction substantiallyparallel to the direction in which the wires it extend from the spoolsit). This movable jig (which is not illustrated in the drawing as it maybe of any suitable design) positions and supports the grid frame 16 sothat the wires extend across the upper surface thereof and contact twooppositely-disposed side members 2! of the frame. The parallel wires 18thus extend across the window area defined by the four side members ofwhich the frame 16 is composed, each of the Wires 18 thus having twopoints of contact with the frame 16. The jig by which the frame 16 issupported causes the latter to contact the wires 18 but at the same timethis contact does not force the wires out of their parallel relationshipor otherwise disturb their normal position.

As previously brought out, the frame 16 is designed to be moved by itssuporting jig in a direction substantially axially or" the wires 18. Inorder to set up the equipment and initiate the operation thereof, afirst frame is placed in such relationship with the wires 18 as to be inthe position A set forth in Figures 2 and 3. In order to properly alignthe wires 18 with respect to the frame 16, a stationary wire-aligningmember 22 is employed between the tensioning apparatus 14 and the firstposition A of the frame. This insures that the wires 18 are parallelwith one another and properly spaced with respect to the side members20. The wire-aligning member 22 preferably consists of a comb-shapedstrip (as best shown in Figure 1) having a plurality of slits equal innumber to the number of wires 18. The latter, after being respectivelydrawn through the slits in the wire-aligning member, then cross theupper surface of the frame 16 lying in the position A (best shown inFigure 2) and then through slits in a second and movable wire-aligningmember 24 which is shown in its raised position in Fig ures 1 and 2.This second wire-aligning member 24 has a function somewhat similar tothat of the first-mentioned wire-aligning member 22 in that it keeps thewires 18 in their parallel position relative to the frame section 16 anddoes not readily permit a displacement thereof even when the wires 13are operated upon during the subsequent welding process. As will laterbe brought out, this second wire-aligning member 24 is arranged to beraised or lowered (as suggested by the dotted outline in Figure 1) topermit a shift of the grid frame 16 from position A to a new position Bshown in Figures 2 and 3.

Summing up, therefore, the plurality of tensioned wires 18 pass throughthe slits in the first wire-aligning member 22, across the upper surfaceof the two oppositely disposed frame members 20, through the slits inthe second wire-aligning member 24 (which is in raised position) andthen to the wire clamp 12 which is utilized to maintain the wire tensionat this stage of operation.

A retaining strip 26 is now laid over the wires 18 so as to extendsubstantially transversely to the direction of the wires and also toextend across the upper surface of one of the frame members 21) (as bestshown in Figure 1) thereby sandwiching the wires 18 between thisretaining strip 26 and the frame member. A pair of diametrically-opposedwelding electrodes 28 are brought into position so that one of theelectrodes exerts a downward pressure upon the upper surface of theretaining strip 26, and the other of the welding electrodes 28 exerts anupward pressure on the undersurface of the frame number 20. Thus thewelding electrodes 28 in effect act to compress therebetween theretaining strip 26, one of the wires 18, and the frame side membernumber 20.

, The welding electrodes 2% are shown in Figures 1 and 2 as being ofsubstantially linear configuration at their effective welding point, andextend substantially normal to the plane defined by the frame 16 and thegrid wires 18. These welding electrodes 28 are furthermore designed tobe movable relative to the assembly consisting of the members 18, 2t)and 26 in a direction substantially transverse to the wires and parallelto the direction of the retaining strip. Expressed still differently,the welding electrodes 28 are designed to travel along the retainingstrip so that current may be passed through the electrodes-28 while theyare centered above each of the wires 18, thus effectively welding one ofthe wires 18 to both the retaining strip 26 and the frame side member20. This relative movement of the electrodes 2-3 is indicated by thearrow in Figure l, and may be carried out by any suitable means.Preferably, the welding electrodes possess a progressive intermittentmovement with respect to the frame 16, this progression being such thatthere is no relative movement of the two elements at the preciseinstants when the welding electrodes 28 are centered above 'each of thewires 18. Current is at those times passed between the electrodes toefiect the weld, following which the current is interrupted and therelative movement between the electrodes 18 and frame 20 continues untilthe electrodes are centered above the next adjacent wire to the one lastwelded. This process continues until all the wires 18 have been weldedto the one particular frame side member 2%. (As shown in Figure 2, twosets of welding electrodes are actually used, but the operation of asingle set has been described above in order to set forth the theory ofoperation.)

In practice, the frame 16 will start in the position A shown in Figure2, so that the first weld will be made on that member 21) which is onthe right hand side of the frame. It is necessary, of course, that thewire clamp 12 be effective during this period in order to retain thewire tension until the first welding operation has been completed.

According to a principal feature of the present invention, the action ofthe retaining strip 26 prevents breakage of the grid wires during thewelding operation. This is due to the fact that each retaining strip 25extends for a sufficient lateral distance to either side of the weldmade by the electrodes 28 so that the tension of the wire being weldeddoes not act to pull it away from the clamped assembly. This resultfollows even though the welding process may possibly cause a melting ofthe wire material to such an extent that the strength of the wire duringthe welding operation would normally be reduced substantially to zero atthe weld point. To accomplish this clamping effect, the width of each ofthe retaining strips 26 is so chosen that the welding current flows onlythrough a portion of the strip width, with the remaining portion servingsolely as a clamp.

After a welding of one of the side members 20 has been completed in theposition A shown in Figure 2, the frame 16 is moved by its jig toposition B. In the latter location, the remaining one of the sidemembers 20 is welded by a second pair of welding electrodes 28.Concurrently with this welding of the remaining side member 20 of theinitial frame 16, a welding of one member of a second frame is carriedout, this second frame being in the position A formerly occupied by theinitial frame (see Fig. 3b). Expressed differently, one side member ofeach of two separate frames is welded in a single welding operation bythe use of the two pairs of welding electrodes 28 shown in Figure 2.Since the operation of each of these pairs of electrodes is identical,it is believed that the above description is sufficient to make thisphase of applicants process completely clear.

Once a welding operation has been completed so that the set of wires 18is secured to one side of a frame member 16, the wire clamp 12 is nolonger necessary and can be dispensed with.

In order to permit the shift of a frame section 16 from position A toposition B, it is necessary that the movable wire-aligning member 24 belowered as indicated in dotted lines in Figures 1 and 2 so that the jigon which the frame 16 is supported may move this frame 16 withouthindrance. Any suitable means of raising and lowering this member 24 maybe used, and since the particular details thereof constitute no part ofthe present invention they have not been illustrated.

Figure 3 shows the successive frame movements from position A toposition B to a final position C. As illustrated in Figure 3a, one weldis initially performed in position A as indicated by the small x on theupper surface of one of the frame side members 29. The frame is thenshifted to position B, and a new frame is brought into position A asshown in Figure 3b. Two welds are then carried out simultaneously, oneof these welds being the final one for the initial frame, and the otherweld being the first one for the new frame member. The initial frame(now being welded in its entirety) is moved to a new position C as shownin Figure 3c. The projecting ends of the grid wires 18 are then shearedoff at the point indicated so that the completed frame assembly afterbeing removed from the welding jig will have the appearance shown inFigure 4. Both retaining strips 26 will overlie the parallel grid wires18, and the Welds will securely hold the retaining strips 26, grid wires18, and

rame 16 in a unitary structure.

if desired, additional welds may be made at or near the extreme ends ofeach retaining strip 26 so as to prevent any looseness between thesemembers and the frame 16 and to result in a better positioning of theassembly during the welding operation.

It will now be recognized that the welding process herein described iscapable of continuous operation so as to mass-produce grid structures ofthe type set forth with a minimum of manual attention and by theemployment of relatively simple and inexpensive apparatus.

Although linear welding electrodes have been illustrated in Figures 1and 2, it is obvious that the particular shape of these elements formsno part of the present invention. For example, if desired the weldingelectrodes may have a configuration such as shown in Figures and 6. Thatis, they may be substantially cylindrical in outline so as to permit arolling movement of the electrodes over the retaining strips 26 and theframe sections 20. These roller electrodes, identified by the referencenumeral 3t), are of a type known in the art, and, as in the case ofFigures 1 and 2, serve to compress the retaining strips 26, the gridwires 18, and the frame sections 29 therebetween and thus preclude anylateral displacement of the grid wires 18 relative to the membersbetween which they are compressed. In the case of the modification shownin Figures 5 and 6, it may be desirable to apply a continuous weldingcurrent to the electrodes 3t or it may be preferable intermittently tointerrupt the current and permit it to flow only at the times when theaxis of each of the roller electrodes 30 is substantially in line withone of the grid wires 18 (as best shown in Figure 5). The particulartype of operation utilized will depend in part upon the composition ofthe materials used, upon their thickness, and upon the conditions underwhich the resulting structure is to be operated. Either mode ofoperation is clearly within the scope of the present disclosure.

Although the present invention is not limited to use with any particulartype of frame section or with any particu lar type and size of Wire,nevertheless one arrangement which has operated successfully in actualpractice employs stainless steel wire having a diameter of approximately6 mils, a. rectangular frame section made out of A thick stainlesssteel, and retaining strips also made of stainless steel and having athickness of approximately 6 mils. These dimensions, however, areintended to serve merely as examples, and will be modified as determinedby practical considerations.

Having thus described the invention, What is claimed is:

l. In the art of welding a plurality of tensioned wires to a frame madeup of two sets of oppositely-disposed sections so that the wires extendin substantially parallel relationship across the window area defined bythe two sets of o positely-disposed sections, the steps which includelriC-lllilg said tensioned wires so that they have substantially therelative positions desired after welding, bringing said frame intocontact with said Wires so that each particular wire of the lattercontacts two oppositelydisposed frame sections, spot-welding each wireto each of the two said oppositely-disposed frame sections, andcompressing said wire during the Welding operation against Fur thatparticular frame section which is being welded for a sufficient distancealong said wire in each direction from the welding area so that thetension in said wire across the window area of said frame is retainedregardless of the detensioning effect induced by softening of the Wirematerial as a result of the welding operation.

2. A process according to claim 1, in which all of said plurality ofwires are welded to said frame in consecutive fashion, and in which thecompressing of said each wire against a particular frame section isperformed by a retaining strip of electrically-conductive materialextending substantially transversely to and overlying said wires in sucha. manner that the latter are sandwiched between said retaining stripand said frame section.

3. A process according to claim 2, in which each wire of said pluralityis welded to said frame section through the medium of a pair ofoppositely-disposed welding electrodes which have a unitary movementrelative to said frame section in the general direction of saidretaining strip, the two electrodes of said pair respectively contactingsaid retaining strip and said frame section.

4. A process according to claim 3, in which the relative movement ofsaid welding electrodes and said frame section is of a continuousnature.

5. A process according to claim 3, in which the relative movement ofsaid welding electrodes and said frame section is of an intermittentnature.

6. A method of welding a filamentary conductor under tension to ametallic supporting member which includes the step of clamping saidconductor to said supporting member beyond the welding area so that suchclamping action tends to maintain the tensioned condition of saidconductor when the substance of which the latter is composed tends tochange its nature during the welding operation.

7. The process of welding a plurality of tensioned wires to a supportingframe so that they extend across an opening therein, said processincluding the steps of positioning said frame so that said wires lieacross one surface thereof, placing an elongated retaining member oversaid wires so that the former extends substantially transversely to thedirection of said wires, connecting a welding current source between apair of linear electrodes, bringing the assembly consisting of saidframe, said wires and said retaining member between said electrodes, andcreating a relative movement between said pair of electrodes and saidretaining member and in the general direction of the latter so that bythe current from the source the said wires are successively welded tosaid frame.

8. The process of welding a plurality of tensioned wires to a supportingframe so that they extend across an openi rig therein, said processincluding the steps of positioning said frame so that said wires lieacross one surface thereof, placing an elongated retaining member oversaid Wires so that the former extends substantially transversely to thedirection of said wires, connecting a current source between a pair ofroller electrodes, bringing the assembly consisting of said frame, saidWires and said retaining member between said electrodes, and creating arelative movement between said pair of electrodes and said rerainingmember and in the general direction of the latter so that current fromthe source is effective to Weld said wires successively to said frame.

Cited in the file of this patent UNITED STATES PATENTS 1,066,536 DeanOct. 24, 1911 2,479,556 Chanowitz Aug. 23, 1949 FOREIGN PATENTS 355,662Germany June 29, 1922 388,076 Germany Jan. 8, 1924

